1. Field of the Invention
The present invention relates to a microscope objective lens.
2. Description of the Related Art
In the field of microscopes, there has conventionally been a demand for the ability to observe cultured cells at high resolution. In order to meet this demand, a microscope objective lens having a high numerical aperture and a relatively low magnification is needed. A microscope objective lens that can meet this demand is disclosed by, for example, Japanese Laid-open Patent Publication No. 5-119264.
The objective lens disclosed by Japanese Laid-open Patent Publication No. 5-119264 has a high numerical aperture of 0.7 while having 20× magnification. Further, this lens realizes a high flatness of the field.
For observation of cultured cells, a cover glass, a dish, and the like (these items are referred to as a group as cover glass hereinafter) are usually used, and the thickness of the cover glass varies depending upon the specification, the production errors, etc. The variation in thickness of a cover glass causes variations in spherical aberrations in the field, leading to deteriorations in the observation performance. Accordingly, a microscope objective lens having a correction collar, for correcting variations in spherical aberrations caused by variations in thickness of a cover glass, is desired.